In a gamble with a friend, you are to bet whether the coin they are hiding behind their back is fair or has heads on both sides. You begin by assessing that the probability that the coin if fair is 1/2, to express the fact that you have no reasons to believe that one scenario is more likely than the other. So, 1/2 is your prior probability. To help you out, your friend tosses the coin and informs you that the outcome is heads. Compute the conditional probability that the coin is fair given this event. This is your posterior probability, whereby you update your original beliefheld prior to observing any evidencein light of new data. If you were to enter the game now, would you bet that the coin is fair?